Series Finale:     
Episode 45 – The Great Leap Forward
Tom (Joel Gretsch) is put into a truck where Diana (Jacqueline McKenzie), Meghan (Jenni Baird), Marco (Richard Kahan), and Shawn (Patrick Flueger) are waiting. Marco injects Tom with Polonium that burns the nano-machines inside him and destroys the body snatcher. The process ultimately kills him but Shawn saves Tom by healing him. Tom still retains all of the memories from being marked and is horrified about what he’s done. He tells Diana and Meghan that he needs to go back to free Collier. Because they believe he’s marked, Tom says that he’s the only one who can succeed.

Danny (Kaj-Erik Eriksen) goes with his mother (Chilton Crane) to the hospital. He notices that people begin to exhibit the same symptoms and begin dying, as if they’d taken a promicin injection. Danny realizes that he’s developed the ability to spread promicin like an airborne virus. As a result, he ends up causing hundreds to either die or develop abilities. He goes to the 4400 center to ask for Shawn’s help, to tell him that he is the one responsible for the deaths/abilities, and that their mother has died. Kevin (Jeffrey Combs) gives Danny an inhibitor so that he’s no longer contagious.

Meanwhile, the people of Seattle are being infected. The outbreak wasn’t contained to the hospital and it’s spreading through the police force and the NTAC. The NTAC is forced to work with the Promise City residents to try to control the violence and chaos that is taking place.

Strangely, Diana is the only survivor at NTAC who hasn’t tested positive for promicin. Marco attributes this to the fact that earlier, Kevin had given her a series of promicin shots. This has somehow made her immune to it. She goes to the 4400 center and Kevin determines that an enzyme called ubiquinone is what is allowing her to resist the promicin exposure. Fortunately, the enzyme is contained in a common over-the-counter drug. Diana sends an order to have supplies of the drug made available to those in Seattle who have not yet been exposed to the virus.

Meanwhile, a marked Isabelle (Megalyn Echikunwoke) tracks down Kyle (Chad Faust) who has become the new leader of the Promise City residents. The marked are not pleased. The effects of Danny’s ability are ruining their plans to terminate 4400s and prevent people from gaining abilities. Tom returns to try and free Collier (Billy Campbell) but is unsuccessful. When he hears that Isabelle was sent to kill Kyle, he flinches and gives himself away.

Isabelle resists killing Kyle and instead returns to free Tom and Collier. She kills the marked bodyguards and Rebecca Parrish (Penny Johnson) but is ultimately killed herself. Tom and Collier escape and learn how the city has changed.

Back at the 4400 center, the inhibitor is working on Danny but the promicin is building up in his body. Since it’s no longer being released, it’s slowly killing him. He tells Shawn that he doesn’t want to stop taking the inhibitor because he knows that others will die. He would rather be the last. Danny begs Shawn to kill him and, heartbroken, Shawn complies.

With over 9,000 deaths and as many newly empowered people, Seattle has really changed. We see Meghan turn a pen into a flower, Agent Garrity (Kavan Smith) create an energy-clone of himself, and Marco unintentionally teleport himself from NTAC to Promise City.

Seattle is renamed Promise City and is now under the control of Collier and his followers. Maia remarks to Diana that she believes that it’s better this way. Kyle visits his father and tells him that, even though he has killed people, he must move on and leaves him a shot of promicin.
First aired: September 16, 2007